Lead scavenger compositions



LEAD SCAVENGER COB POSITIONS Jenard E. Yust, Alton, and John L. Bame,East Alton,

HL, assignors to Shell Development Company, Emeryville, Calif, acorporation of Delaware No Drawing. Application July 22, 1952 Serial No.300,337

14 Claims. (Cl. 44-69) This invention relates to compositions which areuseful as scavengers with lead anti-knock compounds.

The use of lead compounds in gasolines to increase the octane ratingsthereof is extremely widespread. There are, however, several ratherserious adverse efiects which accompany the use of leaded gasolines. Oneof these eifects, the deposition of various lead compounds within thecombustion chambers of the engines, has been at least partially remediedby the use of halohydrocarbon scavengers such as ethylene dibromide.Another adverse effect, which has been attributed to the lead anti-knockcompounds, is mis-firing of the engine due to spark plug fouling. Thisspark plug fouling is quite prevalent under conditions of hightemperature engine operation and, particularly in the caseof aircraftengines, is a very serious type of trouble.

It is, therefore, an object of the present invention to overcome theprevious shortcomings arising from the use of leaded gasolines. It is afurther object to provide novel scavenger compositions for use with leadanti-knock compounds and in gasoline fuels. Another object is to providenovel fuel compositions containing said scavenger compositions. Otherobjects will be apparent hereinafter.

it has now been found that the use, as a lead scavenger in stable leadedgasoline fuel compositions, of a mixture of a halohydrocarbon scavengerand of a smaller'arnount of an alkaryl phosphate or phosphite willresult in greatly improved operation of spark ignition internalcombustion engines. More particularly, the use of such scavengercompositions substantially eliminates spark plug fouling, or at leastminimizes such fouling to a point where it is no longer a materialconsideration in engine operation. This outstanding advantage isobtained without having the anti-knock characteristics of the fueldeleteriously aflected by the presence of the scavenger compositions.

The phosphorous compounds in the present scavenger compositions will bereferred to hereinafter as anti-fouling compounds.

The halohydrocarbon scavenger which makes up the major proportion of thescavenger compositions of the present invention may be, for example, anyof the numerous halogen scavenger compounds already known, such asethylene dibrornide and ethylene dichloride (U.S. 2,398,281), acetylenetetrabromide (U.S. 2,490,606), hexachloro-propylene, monoand polyhalopropanes, butanes and pentanes (U.S. 2,479,900 and U.S. 2,479,902),polyhalo alkyl benzenes (U.S. 2,479,901 and U.S. 2,479,- 903), and thelike, having a volatility between about 100 and about 0.1 mm. Hg. at 50C.

The alkaryl phosphates and phosphites of the present invention are theesters of phosphoric and phosphorous acids, respectively. They may bereadily prepared by reacting alkyl phenols with phosphoric acid to formthe phosphates or with phosphorus trichloride to form the phosphites.Examples of suitable alkyl phenols are ortho-, meta-, and para-cresol;2,4- and 2,5-xylenol; 2,4-dimethyl- 6-tert-butylphenol; octyl and nonylphenols prepared by alkylation of phenol with diisobutylene or propylenetrimited States Patent "ice 2,889,212 Patented June 2, 19 5 9 er,respectively. In general, any phenol containing a hydrocarbon side chainof non-aromatic character is a suitable esterifying agent for makingsuitable alkaryl phosphates and phosphites.

The trialkaryl esters are generally the most suitable anti-foulingagents, but the monoand dialkaryl esters as well as mixed esterscontaining only one or two alkaryl groups can also be used.

Of the alkaryl radicals the di-, tri-, and higher polyalkylated aromaticradicals are preferred over the monoalkyl aromatic radicals. Highermolecular weight alkyl groups, up to about 12 or 15 carbon atoms, aredesirable.

The following are a few examples of suitable antifouling additives ofthe present invention: tri-(m-cresyl) phosphate,tri-(2,4-dimethylphenyl) phosphate, tri-(pethylphenyl) phosphate,tri-(2-methyl-4-isopropyl phenyl) phosphate, tri-(p-tert-butylphenyl)phosphate, tri-(2,6-dimethyl-4-tert-butylphenyl) phosphate,tri-(4-methyl-lnaphthyl) phosphate, ethyl di-(p-cresyl) phosphate, 2,6-xylenyl di-(n-butyl) phosphate, di-(2-methyl-4-ethylphenyl) phosphate,mono-(o-cresyl) diacid phosphate, tri- [p-(n-propyl) phenyl] phosphite,tri [p (1,1,3,3-tetramethylbutyl) phenyll phosphite, tri(2,4,6-trimethylphenyl) phosphite, tri-(p-allylphenyl) phosphite,di-(tertamylphenyl acid) phosphite, i-propyl di-(2,5-dimethylphenyl)phosphite, tri-(3,5-dimethylphenyl) phosphite, e C.

While substituents other than hydrocarbon radicals do not adverselyaffect the efficiency of the phosphates and phosphites as anti-foulingagents, it is preferred that the estler groups thereon beunsubstituted'hydrocarbon radica s.

When using the scavenger compositions of the present invention, thetotal amount of halogen scavenger plus anti-fouling agent will generallyfall between about 0.6 and about 1.5 theories, based upon'the leadcontent of the gasoline, but may advantageously be as low as 0.4 or ashigh as 2.0 in some cases. The preferred range is from about 0.9 toabout 1.2 theories.

The ratio of the two components of the scavenger composition is ratherimportant. For example, if the proportion of halogen scavenger presentis too large, excessive wear and corrosion of certain operating parts,such as exhaust valves and valve guides, is noted. If too small aquantity of halogen scavenger is used, the lead deposits are notefiectively scavenged. If too small a quantity of the anti-foulingcompound is used, the spark plug fouling will not be materially reduced;and if too much of that compound is present the amounts of deposits andthe plug fouling are both increased. In general, the theory ratio of thehalogen scavenger or scavengers to the antifouling agents should bebetween about 3:2 and about :1. For best results this ratio should bebetween about 2:1 and about 15:1. As an additional limitation, the totalscavenger mixture and the ratio of components therein should be adjustedso that the anti-fouling compound is present in an amount of betweenabout 0.01 and about 0.6 theories, and preferably between about 0.05 andabout 0.4 theories. Thus for the preferred minimum of 0.05 theory forthe phosphorus anti-fouling agent and the maximum of 2.0 theories oftotal halogen scavenger and anti-fouling agent, it is seen that a ratioof 2.0 to 0.05, namely 40:1 represents a preferred maximum ratio of thesum of the two to the anti-fouling agent. A particularly desirablecomposition comprises 1 theory of the halogen scavenger and 0.1 theoryof the anti-fouling compound. It is preferred that the weightconcentration of the anti-fouling additive in the fuel be kept below0.1%. It is to be understood that more than one of the compounds fromeach class (i.e., halogen scavenger or anti-fouling agent), may housedin any single composi- 3 tion, just so the total quantity of each typefalls within the limits set forth above.

The term theory," when used in conjunction with a halogen scavengercompound, designates the amount of scavenger required to reactstoichiometrically with a given amount of lead anti-detonant so that allof the lead atoms and all of the halogen atoms form PbBr or PbCl Inorther words, a theory of scavenger is an amount which contains twoatomic proportions of halogen for each atomic proportion of lead in theanti-detonant, or, a theory of the halohydrocarbon scavenger is one molof the halohydrocarbon scavenger divided by one-half the number ofhalogen atoms per molecule, for each gram atom of lead in the leadanti-detonant present, and therefore, the number of theories ofhalohydrocarbon scavenger present in a given composition is equal to thenumber of mols of halohydrocarbon scavenger present multiplied byone-half the number of halogen atoms per molecule, for each gram atom oflead in the lead antidetonant present. As applied to the anti-foulingcompounds, the term theory designates the amount required to reactstoichiometrically with the lead so that all of the lead atoms and allof the phosphorus atoms form Pb (PO or, a theory of the phosphorusanti-fouling compound is one mol of the phosphorus anti-fouling compoundmultiplied by two-thirds (that is, two-thirds of a mol of the phosphorusanti-fouling compound), for each gram atom of lead in the leadanti-detonant present, and therefore the number of theories of thephosphorus antifouling compound present in a given composition is equalto the number of mols of the phosphorus anti-fouling compound presentmultiplied by three-halves, for each gram atom of lead in the leadanti-detonant present.

While it is to be understood that the present compositions may beutilized in any leaded gasoline fuel, the compositions are of particularimportance with respect to use in reciprocating internal combustionengine gasoline fuels, and especially such aviation fuels. This is truebecause of the relatively more frequent occurrence of spark plug foulingin aviation engines, with the greater inherent danger to human life inthe case of failures of such engines. In addition to the leadanti-detonant and the scavenger composition, the gasoline fuels, or theconcentrates for addition thereto may also contain corrosion inhibitorsand stabilizers, such as 2,4-dimethyl-6-tertia1'ybutylphenol and otheralkyl phenols, N,N-dibutyl pphenylene diamine, hydroquinone,phenyl-alpha-naphthylamine, N-butyl-p-aminophenol, alpha-naphthol, etc.,dyes and the like.

By the term leaded gasoline, and the terms of similar import, is meant apetroleum fraction boiling in the gasoline hydrocarbon range (betweenabout 50 F. and about 450 F.) to which has been added a small amount,usually between about 1 and about 6 cc. per gallon, of ametallo-organic, usually an organo-lead, anti-knock compound, such as atetra-alkyl lead, e.g., tetra-ethyl lead, tetra-i-propyl lead, etc.

The fuels to which the present scavenger compositions are added arepreferably those which are relatively stable with respect to oxidationor gum formation. The stability may result from the use of stable basestocks such as aviation alkylate, straight run gasoline fractions, orother fractions which have been highly refined to remove olefins, or thestability may result from the use of oxidation stabilizers, such asthose mentioned above. A few of the phosphorus compound anti-foulingagents of the present invention are known to have slight oxidationinhibiting properties, but these properties are very weak. It is muchpreferred that an additional oxidation inhibitor, i.e., a non-phosphorusstabilizer, be used in the present gasoline compositions. Thus, thegasoline fuels to which the present anti-fouling agents are added shouldbe sufiiciently stable that the addition of the normal amount ofanti-fouling agent will have no substantial effect upon the oxidationstability of the fuele.g., the

4 antiafouling' agents will not decrease gum formation in such fuels bymore than about 5 or 10% As indicated above, the scavenger compositionsof this invention are particularly useful in aviation gasoline. By theterm aviation gasoline" is meant a relatively high grade of gasolinefuel used in aviation engines, as distinguished from the lower qualitygasolines, or motor fuels used in automotive engines. Aviation fuelshave a more closely specified boiling range, generally running from aminimum of about 100 F. to a maximum of about 350 F. The octane numberof such fuels is generally in excess of 100. Because of the demand forhigh quality, thermally cracked fractions are never used in aviationgasolines. Catalytically cracked fractions may sometimes be used, butonly after treatment to remove olefins. One of the reasons for therestrictions upon incorporation of cracked gasolines in aviation fuelsis that the oxidation stability of aviation fuels must be much greaterthan that required for motor fuels. For example, when tested accordingto a method such as described in the patent issued to Thomas W. Bartram,U.S. 2,256,187, an aviation fuel base stock will go well beyond 4 or 5hours before the oxygen pressure will have decreased by 5 pounds persquare inch.

The following example is presented as illustrative of the outstandingresults obtained with fuels containing the compositions of the presentinvention.

Example A Franklin 4AC-l76 engine was operated upon a 100/130 gradeaviation fuel containing 4 cc. of tetraethyl lead per gallon of fuel andl theory of ethylene dibromide (EDB) scavenger. The engine was operatedunder lean mixture cruise conditions, but with 5 minutes of rich mixtureidling every half-hour, and the elapsed time before spark plug fouling(as evidenced by the engine mis-firing), was noted.

The test was then repeated using different scavenger It is to beunderstood that the order of mixing the various constituents of thepresent compositions is immaterial. For example, the anti-foulingcompound may be added to a gasoline which already contains the antiknockcompound and halogen scavenger. Likewise, the metallo-organic anti-knockagent, the halogen scavenger and the anti-fouling compound may be firstmixed, stored and handled as a concentrate, and added to the gasoline ata later time. A typical concentrate of this latter type hasapproximately the following composition:

Wt. percent Tetra-ethyl lead 50-65 Ethylene dibromide 25-40 Tricresylphosphate 3-15 Kerosene, inhibitor, dye stabilizer, etc. 3-6

Under other circumstances it may be desirable to mix the halogenscavenger and the anti-fouling agent, or the antrknock agent and theanti-fouling agent, in the desired relative proportions and handle orstore this mixture,

with or without stabilizers, inhibitors, etc., as a concentrate forlater incorporation with the other components of the ultimate fuelcomposition. Thus, a typical suitable scavenger concentrate consistsessentially of ethylene dibromide and tricresyl phosphate in therelative proportions of 25-40 and 315 parts by weight, respectively.

The present application is a continuation-in-part of our copendingapplication, Serial No. 242,309, filed August 17, 1951, now abandonedwhich is in turn a continuation of our application, Serial No. 167,376,filed June 10, 1950, now abandoned.

We claim as our invention:

1. A fuel composition for internal combustion engines consistingessentially of a stable gasoline composition, a minor suificientlyeffective anti-detonant amount of an organo-lead auti-detonant, and ascavenger mixture for said anti-detonant consisting essentially of ahalohydrocarbon scavenger and of a phosphorus compound selected from thegroup consisting of alkaryl phosphates and alkaryl phosphites, eachalkaryl group of which contains from 7 through carbon atoms, saidhalohydrocarbon scavenger and said phosphorus compound being present inamounts such that, where (a) is the number of mols of halohydrocarbonscavenger present multiplied by one-half the number of halogen atoms permolecule, for each gram atom of lead in the lead anti-detonant present,and (b) is the number of mols of the phosphorus compound presentmultiplied by three-halves, for each gram atom of lead in the leadanti-detonant present, the total of (a) plus (b) is from about 0.4 toabout 2.0, (b) is from about 0.01 to about 0.6, and the ratio of (a) to(b) is from about 3:2 to about 40:1.

2. A composition according to claim 1 wherein the phosphorus compound isa tri(alkaryl) phosphate.

3. A fuel composition for internal combustion engines consistingessentially of a stable gasoline composition, a minor suflicientlyeifective anti-detonant amount of an organo-lead anti-detonant, and ascavenger mixture for said anti-detonant consisting essentially of ahalohydrocarbon scavenger and of a phosphorus compound selected from thegroup consisting of alkaryl phosphates and alkaryl phosphites, eachalkaryl group of which contains from 7 through 15 carbon atoms, saidhalohydrocarbon scavenger and said phosphorus compound being present inamounts such that, where (a) is the number of mols of halohydrocarbonscavenger present multiplied by one-half the number of halogen atoms permolecule, for each gram atom of lead in the lead anti-detonant present,and (b) is the number of mols of the phosphorus compound presentmultiplied by three-halves, for each gram atom of lead in the leadanti-detonant present, the total of (a) plus (b) is from about 0.4 toabout 2.0, (b) is from about 0.05 to about 0.4, and the ratio of (a) to(b) is from about 3:2 to about 40:1.

4. A fuel composition for internal combustion engines consistingessentially of a stable gasoline composition, from about 1 to about 6cc.. of tetraethyl lead per gallon of fuel and a scavenger mixture forsaid tetraethyl lead consisting essentially of a halohydrocarbonoscavenger and tricresyl phosphate, said halohydrocarbon scavenger beingpresent in an amount such that the number of mols of halohydrocarbonscavenger multiplied by onehalf the number of halogen atoms permolecule, for each mol of tetraethyl lead present, is about 1.0, andsaid tricresyl phosphate being present in an amount such that the numberof mols of tricresyl phosphate multiplied by three-halves, for each molof tetraethyl lead present, is about 0.1.

5. A fuel composition for internal combustion engines consistingessentially of a stable gasoline composition, from about 1 to about 6cc. of tetraethyl lead per gallon of fuel and a scavenger mixture forsaid tetraethyl lead consisting essentially of a halohydrocarbonscavenger and tricresyl phosphate, said halohydrocarbon scavenger beingpresent in an amount such that the number of mols of halohydrocarbonscavenger multiplied by one-half the number of halogen atoms permolecule, for each mol of tetraethyl lead present, is about 1.0, andsaid tricresyl phosphate being present in an amount such that the numberof mols of tricresyl phosphate multiplied by three halves, for each molof tetraethyl lead present, is about 0.2.

6. A fuel composition for internal combustion engines consistingessentially of a stabilized gasoline, a minor sufficiently effectiveanti-detonant amount of tetraethyl lead and a scavenger mixture for saidtetraethyl lead consisting essentially of ethylene dibromide, ethylenedichloride and tricresyl phosphate, said ethylene dichloride, ethylenedibromide and tricresyl phosphate being present in amounts such that,where (a) is the total number of mols of ethylene dibromide and ethylenedichloride present, for each mol of tetraethyl lead present, and (b) isthe number of mols of tricresyl phosphate present multiplied bythree-halves, for each mol of tetraethyl lead present, the total of (a)plus (b) is from about 0.4 to about 2.0, (b) is from about 0.05 to about0.4, and the ratio of (a) to (b) is from about 3:2 to about 40: 1.

7. A fuel composition for internal combustion engines consistingessentially of a stable gasoline composition, a minor sufiicientlyeifective anti-detonant amount of tetraethyl lead, and a scavengermixture for said tetraethyl lead consisting essentially of ahalohydrocarbon scavenger and tri(2,5-dimethylphenyl) phosphate, saidhalohydrocarbon scavenger and said tri(2,5-dimethylphenyl) phosphatebeing present in amounts such that, where (a) is the number of mols ofhalohydrocarbon scavenger present multiplied by one-half the number ofhalogen atoms per molecule, for each mol of tetraethyl lead present, and(b) is the number of mols of tri(2,5-dimethylphenyl) phosphate presentmultiplied by three-halves, for each mol of tetraethyl lead present, thetotal of (a) plus (b) is from about 0.4 to about 2.0, and (b) is fromabout 0.1 to about 0.2.

8. A composition according to claim 3, wherein the alkaryl groups of thephosphorus compound are polyalkaryl groups.

9. A fuel composition for internal combustion engines consistingessentially of a stable gasoline composition, a minor sufncientlyeffective anti-detonant amount of an organo-lead anti-detonant, and ascavenger mixture for said anti-detonant consisting essentially of ahalohydrocarbon scavenger and of a phosphorus compound selected from thegroup consisting of alkaryl phosphates and alkaryl phosphites, eachalkaryl group of which contains from 7 through 8 carbon atoms, saidhalohydrocarbon scavenger and said phosphorus compound being present inamounts such that, Where (a) is the number of mols of halohydrocarbonscavenger present multiplied by one-half the number of halogen atoms permolecule, for each gram atom of lead in the lead anti-detonant present,and (b) is the number of mols of the phosphorus compound presentmultiplied by three-halves, for each gram atom of lead in the leadanti-detonant present, the total of (a) plus (b) is from about 0.4 toabout 2.0, (b) is from about 0.05 to about 0.6 and the ratio of (a) to(b) is from about 3:2 to about 40:1.

10. A fuel composition for internal combustion engines consistingessentially of a stable gasoline composition, a minor sufiicientlyeffective anti-detonant amount of an organo-lead anti-detonant, and ascavenger mixture for said anti-detonant consisting essentially of ahalohydrocarbon scavenger and of an alkaryl phosphate each alkaryl groupof which contains from 7 through 8 carbon atoms, said halohydrocarbonscavenger and said phosphate being present in amounts such that, where(a) is the number of mols of halohydrocarbon scavenger presentmultiplied by one-half the number of halogen atoms per molecule, foreach gram atom of lead in the lead anti-detonant present, and (b) is thenumber of mols of the phosphate present multiplied by three-halves, foreach gram atom 7 of lead in the lead anti-detonant present, the total of(a) plus (12) is from about 0.4 to about 2.0, (b) is from about 0.05 toabout 0.4, and the ratio of (a) to (b) is from about 3:2 to about 40:1.

11. A composition according to claim 10, wherein the phosphate is atri(alkaryl) phosphate.

12. A composition according to claim 10, wherein the phosphate is atri-hydrocarbon phosphate.

13. A composition according to claim 10, wherein the phosphate istricresyl phosphate.

14. A fuel composition for internal combustion engines consistingessentially of a stable gasoline composition, a minor sufiicientlyefieetive anti-detonant amount of tetraethyl lead and a scavengermixture for said tetraethyl lead consisting essentially of ahalohydrocarbon scavenger and tricresyl phosphate, said halohydrocarbonscavenger being present in an amount such that the number of mols ofhalohydrocarbon scavenger multiplied by one-half the number of halogenatoms per molecule, for each mol of tetraethyl lead present, is about1.0, and said References Cited in the file of this patent UNITED STATESPATENTS 2,155,678 Oosterbout Aug. 25, 1939 2,256,187 Bartram Sept. 16,1941 2,301,370 Cook et a1 Nov. 10, 1942 2,364,921 Shokal Dec. 12, 19442,398,281 Bartholomew Apr. 9, 1946 2,405,560 Campbell Aug. 13, 19462,427,173 Withrow Sept. 9, 1947 FOREIGN PATENTS 421,568 Canada July 18,1944 600,191 Great Britain Apr. 2, 1948

1. A FUEL COMPOSITION FOR INTERNAL COMBUSTION ENGINES CONSISTINGESSENTIALLY OF A STABLE GASOLINE COMPOSITION, A MINOR SUFFICIENTLYEFFECTIVE ANTI-DETONANT AMOUNT OF AN ORGANO-LEAD ANTI-DETONANT, AND ASCAVENGER MIXTURE FOR SAID ANTI-DETONANT CONSISTING ESSENTIALLY OFHALOHYDROCARBON SCAVENGER AND OF A PHOSPHORUS COMPOUND SELECTED FROM THEGROUP CONSISTING OF ALKARYL PHOSPHATES AND ALKARYL PHOSPHITES, EACHALKARYL GROUP OF WHICH CONTAINS FROM 7 THROUGH 15 CARBON ATOMS, SAIDHALOHYDROCARBON SCAVENGER AND SAID PHOSPHORUS COMPOUND BEING PRESENT INAMOUNTS SUCH THAT, WHERE (A) IS THE NUMBER OF MOLS OF HALOHYDROCARBONSCAVENGER PRESENT MULTIPLIED BY ONE-HALF THE NUMBER OF HALOGEN ATOMS PERMOLECULE, FOR EACH GRAM ATOM OF LEAD IN THE LEAD ANTI-DETONANT PRESENT,AND (B) IS THE NUMBER OF MOLS OF THE PHOSPHORUS COMPOUND PRESENTMULTIPLIED BY THREE-HALVES, FOR EACH GRAM ATOM OF LEAD IN THE LEADANTI-DETONANT PRESENT, THE TOTAL OF (A) PLUS (B) IS FROM ABOUT 0.4 TOABOUT 2.0, (B) IS FROM ABOUT 0.01 TO ABOUT 0.6, AND THE RATIO OF (A) TO(B) IS FROM ABOUT 3:2 TO ABOUT 40:1.